Early Exposure to Bacteria Could Protect Babies From Asthma and Allergies

Often, when bringing new babies home from the hospital, our first instinct is to make sure everything in the house is spotlessly clean. But a new study reveals that when babies are exposed to certain allergens and bacteria in their first year of life, they could be protected from having allergies and asthma later.

There has long been a “hygiene hypothesis,” which claims that children who aren’t exposed to infectious agents and bacteria early in life become more susceptible to allergies later because their immune systems have not properly developed. Their bodies confuse harmless microorganisms with more dangerous invaders. The new study, published in the Journal of Allergy and Clinical Immunology, adds another layer to this hypothesis.

Scientists studied children in large cities like Baltimore, Boston, New York and St. Louis. They tested dust samples from the homes of children, focusing especially on those in urban areas where people often believe housing needs to be cleaned up to protect children.

What they found was that inner-city children exposed to cockroach, mouse and cat allergens during their first year of life had less wheezing when they were 3 years old. Children exposed to an even wider variety of bacteria developed fewer allergies and had lower rates of asthma. Finally, children exposed to all of these tested best of all.

“We still believe that in kids with asthma that these allergen exposures are really unhealthy,” said Dr. Robert Wood, the study’s author and chief of allergy and immunology at Johns Hopkins Hospital. “But it would appear that if we cleaned things up as a preventative measure it would backfire terribly.”